1. Field of the Invention
The present invention relates to the technology field of nanocrystals, and more particularly to a non-contact reactor for producing the nanocrystals and a nanocrystals fabrication system having the same.
2. Description of the Prior Art
Quantum dots (QDs) are nanometer-scale semiconductor crystallites composed of elements from groups III-V, II-VI, or IV-VI listed in the periodic table. Zinc sulfide (ZnS), a first discovered semiconductor nanocrystal, is one kind of direct wide-bandgap semiconductor having many outstanding properties, such as the presence of polar surfaces, excellent transport properties, good thermal stability, and high electronic mobility. Besides the zinc sulfide, there has many semiconductor nanocrystals being discovered or developed, including: cadmium selenide (CdSe), lead sulfide (PbS) and indium phosphide (InP).
Quantum dots (QDs) have been broadly applied in different technology fields of life sciences, electronics, optics, electro-optics, and solar energy. Moreover, researchers have reported that the optical properties of light absorption and light emission of QDs are dependent on their elemental compositions, surface-attached ligands, and particle size. So that, compound QDs with different light absorption and light emission characteristics, for example, copper-doped ZnSe and core-shell CdSe/ZnS QDs, are hence researched and developed by changing or modulating the elemental compositions, the surface-attached ligands, or the particle size of QDs. An exemplary method for manufacturing compound QDs has been disclosed in U.S. Pat. No. 7,192,850, which comprises following steps of manufacturing processes:    step (a): providing a first precursor solution containing a group II element and a second precursor solution containing a group VI element, wherein the said group II element can be zinc (Zn), cadmium (Cd), or mercury (Hg);    step (b): heating and mixing the first precursor solution and the second precursor solution for forming a mixed solution having a plurality of cores of quantum dots dispersing therein; and    step (c): adding a third precursor solution containing a group VI element and a forth precursor solution having at least one dopant into the mixed solution alternatively at a fixed time interval, so as to form quantum dots wrapped with dopant; wherein the dopant can be a transitional metal or a halogen element, and the said group II element being oxygen (O), sulfur (S), selenium (Se), or tellurium (Te).
In order to enhance production rate and production yield, QD manufactures often adopt a reactor to expedite the production of QDs manufactured by using the aforesaid steps. FIG. 1 shows a cross-sectional view of a conventional reactor. The said reactor 1′ mainly consists of a reaction vessel 11′ and a heater 12′, wherein an agitator 13′ is disposed in the reaction vessel 11′, and the rotation speed the stirring paddles 131′ of the agitator 13′ is controlled by an external driving and controlling device. It is worth noting that, for mixing the precursor solutions evenly, a deep tube 14′ is used to make precursor solutions be injected into the reactor 1′ and reach a peripheral position of the stirring paddles 131′ where the tangential force is up to a maximum value. However, since the deep tube 14′ is one kind of contact type apparatus, the use of the deep tube 14′ would cause the remains of the precursor solutions or others organic solutions such as tri-n-octylphosphine (TOP) be left on the inner walls of the reaction vessel 11′ and the outside surface of the agitator 13′; eventually, these remains will become the pollution sources of next-batch-produced QDs.
Accordingly, in view of the conventional semiconductor nanocrystals manufacturing reactor showing many drawbacks and shortcomings in practical QD production, the inventors of the present application have made great efforts to make inventive research thereon and eventually provided a non-contact reactor and a nanocrystals fabrication system having the same.